As is known by one skilled in the art, the level of the (primary) RF signals that are received by communication equipment varies, which induces variations of its decoder performances. In order to restrict these variations a piece of communication equipment comprises a signal level adjusting device (or adjuster) comprising a tuner arranged to adjust its (voltage) gain in accordance with control signals to adjust the level of the primary RF signals received by the communication equipment antenna and a demodulator arranged to generate the control signals from secondary signals representative of the adjusted signals output by the tuner.
In the first generation of adjusters the control signal was a continuous voltage applied to a dedicated pin of an analog variable gain amplifier or attenuator (or the like). This control voltage (usually called “AGC (Automatic Gain Control) control voltage”) generally varies between 0 volt and Vcc. This analog gain control offers good results as long as the dynamic range of the gain variations remains narrow, which is rarely the case. Moreover, analog gain control is sensitive to numerous parameters, such as temperature variations, device characteristic variations or signal modulation characteristics.
In order to overcome these drawbacks, a new generation of tuners with a digital adjuster gain control has been proposed. In this new generation of tuners the gain control may be finely driven by a word of at least 8 bits, for instance. This can be done through a bus. But the bus is sensitive to crosstalk with the transmitted RF signals and its use requires a complex protocol between the channel decoder and the micro-controller of the communication equipment. It is also possible to use an analog-to-digital converter (ADC) to convert the AGC control voltage into a digital gain control signal. But this is at the expense of size when the number of bits of the digital gain control is greater than or equal to 8 bits, which is necessary for a fine gain tuning (or adjustment). Detailed examples of the new tuner generation are notably described in the patent documents U.S. Pat. No. 6,324,229 and US 2004/0037377.